In vehicles which utilize a clutch to couple an engine-driven flywheel to the input shaft of a transmission, there is a continuous need to enhance shiftability and to minimize rattle during both idle and drive operations. This can be accomplished by minimizing excessive proportional vibrations in the drive line while in the operating range and by increasing the travel and torque capacity of the clutch.
In order to maintain smooth shiftability conditions, it is desirable to maintain inertia in the system during gear shifts. In order to accommodate a variety of operational parameters, it is desirable to have a damper design with increased flexibility. Current damper designs are generally not configured for a wide range of operating conditions because design envelopes are restricted, as is flexibility in the number of stages and in the types of damping springs utilized. In order to eliminate both idle gear rattle and drive rattle, it is desirable to provide very soft and partially negative spring characteristics with long spring travel at idle as well as large hysteresis characteristics in the nominal driving range. Drive lines have resonances in their operating ranges which should be minimized, if at all possible. These resonances tend to become more pronounced with time and tend to degrade the vehicle in which the drive line is used.